Technical and Conceptual Review on the L5-S1 Oblique Lateral Interbody Fusion Surgery (OLIF51)

Abstract

Lumbar lateral interbody fusion (LLIF) has been gaining popularity among the spine surgeons dealing with degenerative spinal diseases while LLIF on L5-S1 is still challenging for its technical and anatomical difficulty. OLIF51 procedure achieves effective anterior interbody fusion based on less invasive anterior interbody fusion via bifurcation of great vessels using specially designed retractors. The technique also achieves seamless anterior interbody fusion when combined with OLIF25. A thorough understanding of the procedures and anatomical features is mandatory to avoid perioperative complications.

Keywords: Anterior lumbar interbody fusion (ALIF); Minimally invasive surgery; Oblique lateral interbody fusion (OLIF); complication; retrograde ejaculation; vascular injury.

Figure 1.

Preoperative planning. Confirmation of the anatomy around the anterior portion of L5-S1 disc is mandatory using MRI (a, b), abdominal CT angiography (c, d), and reconstructed sagittal CT scan (e,f). (a) The anatomical window should be wide enough (a), and OLIF51 should not be performed when the vessels are congested in front of the disc (b). Abdominal CT angiography provides the information around the L5-S1 disc: (c) Adequate opening with good indication for OLIF51. (d) The left common iliac vein runs over the disc, and the indication for OLIF 51 must be carefully discussed. Confirmation of the relative location of L5-S1 space to the pubic symphysis is also essential in evaluating the preoperative approach to the L5-S1 disc space. If the direction of the L5-S1 disc goes under the pubic symphysis (e), OLIF51 approach is impossible compared with the usual direction (f).

Figure 2.

Patient positioning using (a) tapes or (b) lateral boards. The patient should be fixed using lateral boards or tape. It may be helpful to flex the lower hip for added stability. (c-d) Skin marking. (c) Under fluoroscopic guidance, check and mark the target L5-S1 disc space and the midportion of the disc space, and draw two identical lines: a vertical line projected perpendicular to the floor, and another one extended onto the abdomen in the direction of the disc. (d, e) The incision is made 1-2 finger breadths from the ASIS along the pelvis. The incision can be made in about 3-7 cm in length. The position of the incision depends on the disc level and number of levels.

Figure 3.

Retroperitoneal approach to the L5-S1 disc. After the circumferential sweep around the undersurface of the transversalis, palpate and follow the internal abdominal wall along with the inside of the pelvis (a). Once touch the iliopsoas, the blunt dissection continues anteriorly from the pelvis while searching for the very palpable common iliac artery pulse (b). Once palpate the pulse on the finger pad, move the finger medially by keeping to feel the pulse on the dorsal side of the finger (c). Direct visualization of the iliopsoas muscle and the common iliac vessels should be established in addition to the tactile feeling. (d) The index finger is touching the promontory by feeling the arterial pulse on the dorsal side of the finger.

Figure 4.

Exposure of the L5-S1 disc. (a) Placement of 1st and 2nd blades by laterally retracting the common iliac vessels. (b) The L5-S1 disc exposed using three retractor blades. The 1st and the 3rd blades are fixed using pins. The red dot line indicates the midline of the L5-S1 disc. (c) Intraoperative images of the L5-S1 disc. Only the 1st retractor is fixed to the sacrum. White arrowhead indicates the medial sacral vessels.

Figure 5.

Disc preparation and implant trialing. After the disc preparation (a), the disc space is sequentially distracted (b, c) until adequate disc space height, and foraminal size are obtained as well as determining the size of the cage using fluoroscopy (d).

Figure 6.

Cage installation. (a) A lordotic intervertebral cage put with DBM (demineralized bone matrix). (b) Cage insertion using an obliquely-designed inserter handle. (c, d) Supplemental screws will be inserted through the screw holes in the anterior portion of the cage.

Figure 7.

Representative case of a 65-year-old women with spondylolysis. Radiological assessment showed L5 spondylolysis with adjacent segment disorder at L4-5 with decreased disc height with impaired local lordosis with no central canal stenosis. (a, b) Plain X-ray (c) Sagittal and parasagittal CT reconstruction. Dotted circle indicates the impaired left L5-S1 foramen.

Figure 8.

The patients underwent OLIF51 surgery combined with L4-5 OLIF, followed by posterior pedicle screw fixation using single position procedure with no patient flipping to a prone position. (a, b): Plain X-ray (c) Sagittal and parasagittal CT reconstruction. Dotted circle indicates the impaired left L5-S1 foramen, and note that the foraminal area enlarged compared with the Fig. 7 (c).